From: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
peterz@infradead.org, mingo@redhat.com,
paulmck@linux.vnet.ibm.com, waiman.long@hpe.com,
xinhui.pan@linux.vnet.ibm.com,
virtualization@lists.linux-foundation.org
Subject: [PATCH v7 1/6] pv-qspinlock: use cmpxchg_release in __pv_queued_spin_unlock
Date: Mon, 19 Sep 2016 05:23:52 -0400 [thread overview]
Message-ID: <1474277037-15200-2-git-send-email-xinhui.pan@linux.vnet.ibm.com> (raw)
In-Reply-To: <1474277037-15200-1-git-send-email-xinhui.pan@linux.vnet.ibm.com>
cmpxchg_release() is more lighweight than cmpxchg() on some archs(e.g.
PPC), moreover, in __pv_queued_spin_unlock() we only needs a RELEASE in
the fast path(pairing with *_try_lock() or *_lock()). And the slow path
has smp_store_release too. So it's safe to use cmpxchg_release here.
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
kernel/locking/qspinlock_paravirt.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index 8a99abf..ce655aa 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -544,7 +544,7 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock)
* unhash. Otherwise it would be possible to have multiple @lock
* entries, which would be BAD.
*/
- locked = cmpxchg(&l->locked, _Q_LOCKED_VAL, 0);
+ locked = cmpxchg_release(&l->locked, _Q_LOCKED_VAL, 0);
if (likely(locked == _Q_LOCKED_VAL))
return;
--
2.4.11
next prev parent reply other threads:[~2016-09-19 5:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-19 9:23 [PATCH v7 0/6] Implement qspinlock/pv-qspinlock on ppc Pan Xinhui
2016-09-19 9:23 ` Pan Xinhui [this message]
2016-09-19 9:23 ` [PATCH v7 2/6] powerpc/qspinlock: powerpc support qspinlock Pan Xinhui
2016-09-19 9:23 ` [PATCH v7 3/6] powerpc: pseries/Kconfig: Add qspinlock build config Pan Xinhui
2016-09-19 8:40 ` kbuild test robot
2016-09-19 9:23 ` [PATCH v7 4/6] powerpc: lib/locks.c: Add cpu yield/wake helper function Pan Xinhui
2016-09-22 15:17 ` Boqun Feng
2016-09-19 9:23 ` [PATCH v7 5/6] powerpc/pv-qspinlock: powerpc support pv-qspinlock Pan Xinhui
2016-09-19 9:23 ` [PATCH v7 6/6] powerpc: pSeries: Add pv-qspinlock build config/make Pan Xinhui
2016-09-19 8:58 ` kbuild test robot
2016-09-22 5:54 ` xinhui
2016-09-22 10:31 ` Michael Ellerman
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